Regulatory Matters - Regulatory Assets (Details) - USD ($) $ in Millions	Dec. 31, 2020	Dec. 31, 2019
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	$ 6,195	$ 4,859
Regulatory assets – current	266	128
Total Regulatory Assets	6,461	4,987
Regulatory assets not earning return	4,766	3,799
Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	3,241	2,541
Regulatory assets not earning return	3,241	2,541
Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	865	732
Regulatory assets not earning return	855	727
Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	356	321
Regulatory assets not earning return	336	296
Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	315	71
Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	241	219
Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	195	77
MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	188	248
System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	124	131
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	120	83
Regulatory assets not earning return	120	83
COVID - 19 Deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	115	0
Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	62	75
Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	36	39
Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	32	35
Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	25	19
Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	21	28
Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	21	22
Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	20	21
Non-wire alternative projects
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	18	14
Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	3
Regulatory assets not earning return	0	3
Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	200	180
Regulatory assets not earning return	24	21
Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	190	128
Regulatory assets not earning return	190	128
Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	76	0
CECONY
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	5,745	4,487
Regulatory assets – current	244	113
Total Regulatory Assets	5,989	4,600
Regulatory assets not earning return	4,481	3,546
CECONY | Unrecognized pension and other postretirement costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	3,065	2,403
Regulatory assets not earning return	3,065	2,403
CECONY | Environmental remediation costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	791	647
Regulatory assets not earning return	781	647
CECONY | Revenue taxes
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	342	308
Regulatory assets not earning return	323	285
CECONY | Pension and other postretirement benefits deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	272	47
CECONY | Property tax reconciliation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	239	210
CECONY | Deferred storm costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	83	0
CECONY | MTA power reliability deferral
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	188	248
CECONY | System peak reduction and energy efficiency programs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	124	130
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	111	76
Regulatory assets not earning return	111	76
CECONY | COVID - 19 Deferrals
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	113	0
CECONY | Municipal infrastructure support costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	62	75
CECONY | Brooklyn Queens demand management program
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	36	39
CECONY | Meadowlands heater odorization project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	32	35
CECONY | Gate station upgrade project
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	25	19
CECONY | Unamortized loss on reacquired debt
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	19	26
CECONY | Preferred stock redemption
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	21	22
CECONY | Recoverable REV demonstration project costs
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	18	19
CECONY | Non-wire alternative projects
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	18	14
CECONY | Workers’ compensation
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	0	3
Regulatory assets not earning return	0	3
CECONY | Other
Regulatory Assets [Line Items]
Regulatory assets – noncurrent	186	166
Regulatory assets not earning return	24	20
CECONY | Deferred derivative losses
Regulatory Assets [Line Items]
Regulatory assets – current	177	113
Regulatory assets not earning return	177	112
CECONY | Recoverable energy costs
Regulatory Assets [Line Items]
Regulatory assets – current	$ 67	$ 0